In We Were Liars, Cadence suffers from a type of memory loss referred to in the novel as selective amnesia. Selective amnesia is one component of dissociative amnesia disorder, a medical condition usually caused by stress or trauma.
The most commonly diagnosed dissociative disorder, dissociative amnesia is distinguished from regular forgetfulness by the information forgotten, which tends to be sensitive or traumatic. In some cases, stressful events may lead people to forget autobiographical details like their name, profession, or where they live.
The Diagnostic and Statistical Manual of Mental Disorders identifies several types of amnesia that people with the disorder experience. With localized amnesia, a person can't remember a certain event or series of events, such as abuse that occurred in a given period. Selective amnesia, which can occur alongside localized amnesia, is the term for when someone loses certain parts of their memory, but not the entirety of an event. With continuous amnesia, a traumatic event may lead someone to forget new information as they experience it. Systematized amnesia involves the loss of memories associated with a particular person, such as someone who caused the sufferer harm. A rarer variety of amnesia, generalized amnesia involves forgetting one's identity and even skills they have established proficiency in. The DSM also identifies dissociative fugue as a possible but very rare symptom of dissociative amnesia disorder. In an episode of dissociative fugue, which can last from hours to months, a person might wander from their home and fail to recognize people they know. They may even assume a new identity during the fugue, appearing to act normal but forgetting their past life completely.
While researchers have not found the exact cause of dissociative amnesia disorder, its relationship to trauma has been demonstrated. People who have lived through traumatic events such as sexual assault, natural disasters, and military combat are among the most commonly diagnosed. Common treatments include hypnotherapy, cognitive behavioral therapy, eye movement desensitizing and reprocessing, and dialectical behavioral therapy. If a patient is removed from the stressful situation that induced the disorder, treatment can usually help them recover their memory.
